全文获取类型
收费全文 | 4440篇 |
免费 | 818篇 |
国内免费 | 507篇 |
专业分类
化学 | 3351篇 |
晶体学 | 40篇 |
力学 | 216篇 |
综合类 | 47篇 |
数学 | 484篇 |
物理学 | 1627篇 |
出版年
2024年 | 5篇 |
2023年 | 74篇 |
2022年 | 114篇 |
2021年 | 124篇 |
2020年 | 178篇 |
2019年 | 193篇 |
2018年 | 155篇 |
2017年 | 128篇 |
2016年 | 237篇 |
2015年 | 208篇 |
2014年 | 257篇 |
2013年 | 301篇 |
2012年 | 372篇 |
2011年 | 375篇 |
2010年 | 275篇 |
2009年 | 300篇 |
2008年 | 313篇 |
2007年 | 274篇 |
2006年 | 258篇 |
2005年 | 231篇 |
2004年 | 170篇 |
2003年 | 145篇 |
2002年 | 181篇 |
2001年 | 153篇 |
2000年 | 92篇 |
1999年 | 107篇 |
1998年 | 73篇 |
1997年 | 61篇 |
1996年 | 70篇 |
1995年 | 44篇 |
1994年 | 56篇 |
1993年 | 32篇 |
1992年 | 20篇 |
1991年 | 42篇 |
1990年 | 38篇 |
1989年 | 29篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 11篇 |
1985年 | 19篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1970年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
1962年 | 1篇 |
1959年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有5765条查询结果,搜索用时 31 毫秒
991.
Junhai Liu Chenlin Du Zhengping Wang Li Zhu Huaijin Zhang Xianlin Meng Jiyang Wang Zongshu Shao Minhua Jiang 《Optics & Laser Technology》2001,33(3)
A diode-pumped acousto-optically Q-switched intracavity frequency-doubled Nd:GdVO4/KTP green laser formed with a flat–flat resonator was demonstrated. 3.05 W of average green output power at pulse repetition frequency (PRF) of 40 kHz was obtained with an optical conversion efficiency of 18.4%, the effective intracavity frequency-doubling efficiency was 57%. At the incident pump power of 15 W, the shortest laser pulse occurred at PRF of 25 kHz with FWHM width of 14 ns, yielding the highest peak power of 7.44 kW; while the largest pulse energy of 0.14 mJ was achieved at PRF of 15 kHz. 相似文献
992.
Zhengping Wang Lianke Sun Shaojun Zhang Xianlin Meng Ruiping Cheng Zongshu Shao 《Optics & Laser Technology》2001,33(1):63
The absorption properties of Nd:YVO4 crystals with various doping levels and lengths are reported. The effective stimulated emission cross-sections of different doping levels are calculated with measured upper-level lifetimes. Our investigation gives good advice on the optimization of LD end-pumped Nd:YVO4 laser. 相似文献
993.
Guangyong Zhou Xiaomei Wang Dong Wang Chun Wang Zongshu Shao Qi Fang Minhua Jiang 《Optics Communications》2001,190(1-6):345-349
Trans-4-[p-(pyrrolidinyl)styryl]-N-methylpyridinium iodide (abbreviated as PSPI thereafter) is a two-photon absorption (TPA) dye newly synthesized by our research group. It possesses much larger TPA cross-section and much stronger upconversion fluorescence emission than those of common organic dye (such as rhodamine) when excited with near infrared (IR) radiation. TPA spectrum and upconversion efficiency spectrum of HEASPI solution at various wavelengths were measured. There is 34 nm blue shift for the central wavelength of the TPA induced absorption peak compared with two times of the linear absorption peak. The biggest molecular TPA cross-section σ2′ is 2.85×10−47 cm4 s/photon at 930 nm. At 1064 nm, σ2′ is 3.12×10−48 cm4 s/photon. The highest efficiency is 3.9% at 1010 nm, whereas 2.9% at 1064 nm. Its optical power limiting properties at 930 nm have also been illustrated. 相似文献
994.
Z. Wang K. Fu X. Xu X. Sun H. Jiang R. Song J. Liu J. Wang Y. Liu J. Wei Z. Shao 《Applied physics. B, Lasers and optics》2001,72(7):839-842
A method of determining the spatial configuration of a YCa4O(BO3)3 (YCOB) crystal is introduced. The type-I phase-matching points for the sum-frequency of 1.064 μm and 0.532 μm, as well as
the conversion efficiency for YCOB samples cut in different directions, have been measured. When the input intensity is 0.76 GW/cm2, the third-harmonic generation (THG) conversion efficiency for the (106°, 77.2°)-cut YCOB crystal reaches 26.2%, which is
the highest that we know so far. Both the calculations and the experiments show that the optimum THG configuration for a YCOB
crystal is near (106°, 77.2°), or other equivalent directions in space.
Received: 11 September 2000 / Revised version: 25 January 2001 / Published online: 27 April 2001 相似文献
995.
金刚石锯片在锯切过程中的受力与失效分析 总被引:2,自引:0,他引:2
对金刚石锯片在锯切过程中的受力及弧区内直接参与切削的金刚石数量进行了测量和估算,并分析了节块表面抛光和微破碎金刚石比例与锯片寿命和效率之间的关系,结果表明:单颗粒金刚石的受力远低于其静压强度;其低强度失效的原因是锯切过程中金刚石晶体内产生的热应力。 相似文献
996.
本文利用文献 [1 ]中的结果给出了张量空间中多面体锥的性质 ,指出当 K1,K2 分别为 V1,V2中的多面体锥时 ,由它们所生成的 V1 V2 中的最小真正锥也是多面体锥 ,这一条件不仅是充分的也是必要的 .并利用这一结果对多面体锥的已有结论给出了新的证明 相似文献
997.
998.
999.
This paper is part of our efforts to develop Stein's method beyond uniform bounds in normal approximation. Our main result
is a proof for a non-uniform Berry–Esseen bound for independent and not necessarily identically distributed random variables
without assuming the existence of third moments. It is proved by combining truncation with Stein's method and by taking the
concentration inequality approach, improved and adapted for non-uniform bounds. To illustrate the technique, we give a proof
for a uniform Berry–Esseen bound without assuming the existence of third moments.
Received: 2 March 2000 / Revised version: 20 July 2000 / Published online: 26 April 2001 相似文献
1000.
We study the quantum dynamics of a single-Cooper-pair box biased by a classical voltage and also irradiated by a single-mode quantized field. We demonstrate that under weak damping of the quantized field, the collapse-revival phenomena can exist in this system, and the oscillations of the collapse and revival depend sensitively on the initial state of the single-mode quantized field and the damping rate κ. We also demonstrate that this system can show the beats phenomena. 相似文献